XC161 Datasheet, PDF (173/419 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller with C166SV2 Core Volume 2 (of 2): Peripheral Units

XC161 Derivatives
Peripheral Units (Vol. 2 of 2)
Asynchronous/Synchronous Serial Interface (ASC)
In general, the baudrate generator in Asynchronous Mode is build up by two parts (see
also Figure 18-14):
• The clock prescaler part which derives f_DIV from f_ASC
• The baudrate timer part which generates the sample clock f_BRT and the baudrate
clock f_BR
Prior to an Autobaud Detection the prescaler part has to be set up by the CPU while the
baudrate timer (register ASCx_BG) is initialized with a 13-bit value (BR_VALUE)
automatically after a successful autobaud detection. For the following calculations, the
fractional divider is used (FDE = 1).
Note: It is also possible to use the fixed divide-by-2 or divide-by-3 prescaler. But the
fractional divider allows the much more precise adaption of f_DIV to the required
value.
Standard Baudrates
For standard baudrate detection the baudrates as shown in Table 18-8 can be e.g.
detected. Therefore, the output frequency f_DIV of the baudrate generator must be set to
a frequency derived from the module clock f_ASC in a way that it is equal to 11.0592 MHz.
The value to be written into register FDV is the nearest integer value which is calculated
according the following formula:
FDV = ^{5----1---2-----×}-----1---1----.-0----5---9---2-----M-----H-----z-
f_ASC
(18.1)
Table 18-8 defines the nine standard baudrates (Br0 - Br8) which can be detected for
f_DIV = 11.0592 MHz.
Table 18-8
Baudrate
Numbering
Br0
Br1
Br2
Br3
Br4
Br5
Br6
Br7
Br8
Autobaud Detection Using Standard Baudrates (f_DIV = 11.0592 MHz)
Detectable Standard Divide Factor d_f BG is Loaded after
Baudrate
Detection with Value
230.400 kbit/s
115.200 kbit/s
57.600 kbit/s
38.400 kbit/s
19.200 kbit/s
9600 bit/s
4800 bit/s
2400 bit/s
1200 bit/s
48
96
192
288
576
1152
2304
4608
9216
2 = 002_H
5 = 005_H
11 = 00B_H
17 = 011_H
35 = 023_H
71 = 047_H
143 = 08F_H
287 = 11F_H
575 = 23F_H
User’s Manual
ASC_X, V2.0
18-30
V2.2, 2004-01